Well I have a pretty modest set-up at home - it's all in my sig - NFB-12 or NFB-12 to an LD MKIV. Nothing really fancy. The great thing about the HD700 though is how easy it is to drive. I was away for the weekend to visit family, and took my uDac3 and laptop - but in the end used them mostly straight out of my iPhone4. Sounded great and I didn't feel I was missing anything.
Your E17 should be fine. I wouldn't sweat it. Spend the money you save on music - that's where I get the most enjoyment